Here's that question

Just say, "I'm sorry, I don't think we're a good match."..

The same way you'd tell someone that you're dating IRL -- you can either lie, or be honest. Little white lies are handy in this sort of situation: "I've met someone else I really clicked with" or "I'm deathly allergic to your cologne/cat/body hair." Or you can just tell them that it's not really working for you, that they're sweet but there's no chemistry, or that you don't see a future with them. Chances are that if you're not feeling the love, they aren't either, and the rejection won't be all that hard for them to take...

I found that one way guys in the big city do it is to just disappear! They emerged out of thin air then they return back to it, since you have no shared social ties. They just don't call or email, and that's the end of that. That's one of the things I hate about online dating. I'd say, anything is better than that! Just the basic "I didn't feel a connection" should do it...

Yea just do it the same way as you would in real life..."I do not think we make a good match." "We don't have much in common" the usual cliche things...